# Creating a column vector for each variable in a for loop?

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Bob on 13 Dec 2014
Commented: Christof Omar on 20 Dec 2017
Here is my code:
D=[1 4 7 5];
for i=1:length(D)
A=D(1,i)
B=A+3
C=B-5
end
How do I create a column vector of values for each variable in the for loop (I want a column vector for all the A values, another column vector for all the B values, and one last column vector for all the C values?

Guillaume on 13 Dec 2014
You would just index into the destination variables in the for loop, the same way you index into the origin vector. Optionally, you would also predeclare the outputs:
D=[1 4 7 5];
A = zeros(numel(D), 1);
B = zeros(numel(D), 1);
C = zeros(numel(D), 1);
for i = 1 : numel(D)
A(i, 1) = D(i); %or simply A(i) = D(i), if A is predeclared
B(i) = A(i) + 3;
C(i) = B(i) - 5;
end
However, for arithmetic operations like that, you shouldn't use a for loop and just operate on the whole vector at once. Since you start with a row vector and want columns vector, at some point you need to transpose the result:
A = D.';
B = A + 3;
C = B - 5;
Christof Omar on 20 Dec 2017
Thank you, that helped a lot!

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